Process for separating hydrocarbon waxes



March 1, 1955 Filed May 20, 1952 A. A. SCHAERER PROCESS FOR SEPARATING HYDROCARBON WAXES F'rzopr-zznes OF PAKAFFIN WAXES Boiling Poin+ C: a+ l mm Hg 56 8.53m (For n From lei-056) Normal Pamfiins Boili Poin+ Curves MeH-in sh-ai hat PamQ-Hns n Mel nq Pair-1+ 1.4 n

L5 NUMBER OF- C-ATOMS PER MOLECULE \nvenror 2 Sheets-Sheet 1 Somme POINT, c AT 15 mm Ha AL: us+ Achaerer m m M e His AH'orneL;

March 1, 1955 A. A. SCHAERER PROCESS FOR SEPARATING HYDROCARBON WAXES 2 Sheets-Sheet 2 Filed May 20, 19 s2 Souuenurv OF rl-PARAFFINS m METHYL \SOBUTYL. KETQNE 0 IO 10 so 40 so so TEMPERATURE ,"c.

Hall

SOLUEILITIES OF- PARAFFKN WAXES nu METHYL ETHYL. KETONE 10 7.0 TEMPERATURE ,c.

F-lc. III

a a u a 8 h 500 .A IT A WUM-S T 4 nu WA U .m b

after addition of a solvent and/or diluent. on the nature of the oil and the conditions of the opera United States Patent PROCESS FOR SEPARATING HYDROCARBON WAXES This inventionflrelates to "the-art of separating hydrocarbon waxes. More particularly-it pertains to the separation and recovery of various types of hydrocarbon waxes from mixtures thereof. Still more specifically, it pertains to the separation from waxy mineral oil stocks, including such stocks as contain a predominant proportion of paraffin wax such as of the character of slack wax and the like, of normal orstraight-chain parafiin waxes contained therein, separately from non-straight chain or isomeric -(isoand cyclo-) paraflin waxes also contained therein.

Various methods have been used and suggested for the recovery and/or fractionation of paraflin waxes from mineral oil stocks. Thus, it is known to dewax waxy mineral oils 'or'fractions thereof by cooling, sometimes Dependent tion, such as lowest cooling temperature, rate ofcooling,

manner of cooling, etc., the paraffin wax'thus obtained has been either in the form of readily filterable crystals or of a poorly' filterable, microcrystalline or amorphous usually obtained in connection with dewaxing operations as applied to paraifinic lubricating oil distillate stock and consist largely of high molecular weight aliphatic or parafiinic hydrocarbons with a straight chain, i. e. n -parafiins, whereas'the-microcrystalline or amorphous product. *The crystalline readily filterable,-products are *productsconsist, at least to'a large and controlling extent, of high molecular weight aliphatic hydrocarbons of a branched character, including branched-chain and'ringcontaining hydrocarbons, generally termed isoparafiins and cycloparaffins, respectively, both classes of which may be termed as isomeric parai'lins (relative to the n-paraffins). Frequently occurring cycloparafiins in mineral oils are paraffins having a naphthenic ring, generally of five or's'ixc'arbon atoms per ring, to which is bound a'straight or branchedaliphatic hydrocarbon chain. Waxes obtained'by the usual 'dewaxing operations, with or without the aid of solvents and/or diluents, generally contain appreciable proportions of oil. These waxes are usually dc-oiled by a so-called sweating and filtering process and/ or a" solvent de-oiling process.

' The n-parafiin" hydrocarbonwaxes on the'one hand and the non-straight-chain parafiin hydrocarbon waxes on the other hand have properties-which in many respects are widelydivergent. These diiferences in properties account, for example, for the difierences in applications or utility .of the n-paraflin' waxes and the isomeric parafiin waxes.

Thus, for "instance, normal paraffin waxes having at least 22 carbon atoms per molecule are particularly suitable for the manufacture of candles (candle wax) and parafiin paper; while the isomeric ('iso-' and cyclo-) parafiin waxes,

especially those'having more than approximately 26 carbonatoms per molecule, in an oil-free state, form useful products on account of their plastic properties and adhesion to glass and to metal articles.

. In view of the differences in properties between straight chain ornormal'paraffin waxes on the one hand, and the lsomeric paraffin waxes on the other hand, it is desirable and, therefore, an object of this invention to provide an improved process wherebythey may be obtained from waxypetroleum'stocks and separately from each other.

A further object is to provide an improved process for the separation'of n-paraffin waxes from isoand/ or cycloparafiin waxes and/or from oils in'admixture therewith, and at the same time to separate the n-parafiin waxes into variousfractions thereof a approximating .those of. single molecular species.

Another object of the invention is 'to r 2,703,305 Patented ..Ma.r. 1, .1955

I process for de-oiling oily waxes and separating and recovering the waxes -as desirable fractions 'of n-paratfinic hydrocarbon=waxes and of isoand/or cyclo-parafiinic hydrocarbon waxes.

The foregoing objects will 'be better understood and others will become apparent from the following description of the invention, which will bemade with reference to the accompanying drawing, wherein:

Fig.1 is a graphical'representation of the relationships between the boiling points, the'melting points and the number of carbon atoms per molecule of parafiin hydrocarbons containing from 20 to 35 carbon atoms per molecule;

Fig. II shows graphically the solubility-temperature relationships of various normal paraffin Wax hydrocarbons in methyl isobutyl ketone;

Fig. 111 shows graphically the solubility-temperature relationships in methyl ethyl ketone of three waxes having the same melting point, 'buthaving different molecular weights.

It has now been found that normal (i. e., straightchain) paraffin waxes can'be separated from other (i. e., isoand cyclo-) parafiin waxes in mixtures thereof, particularly extending over the range of C20 to C35 hydrocarbons, by'a combination of operations which comprises fractionating the given'mixture into a number of fractions according to melting or freezing point, as by'fractional crystallization, preferably in the presence of a solvent 'or diluent, at least one fraction of which has a relatively narrow melting point range' (a range of about 4 C. to about 12 C.), 'and contains both straight-chain and non-straight chain -paraifins Within that'melting point range, the straight-chain hydrocarbons within that melting point rangehaving'a relatively-small range of carbon atoms per-molecule (3 to '4), and fractionatingat least tially of thenon-straight=chainparaffin hydrocarbons. It

is also-contemplated tofractionatethe second fraction according 'to molecular'weight to separate the lower molecular'weight non-straight-chain parafiin hydrocarbons 'present therein from higher'molecular weight, nonstrai'ght-chain paraflins present.

In accordance'with'a preferred embodiment of the invention, the-waxy mixture is fractionally crystallized, preferably in the presenceof a solvent, into a plurality of fractions havingnarrow'melting point ranges, respectively, 'and each fraction isthen'fractionally distilled to producefrom each:fraction' a first, lower'boiling point, lower molecular weight, fraction, composed substantially entirely of at least asubstantial portion up to substantially 'all of the straight-chain parafiin hydrocarbons present in the particular fraction thus fractionated. Still furtherythememaining portion of each'fraction so fractionated can be fractionated to-separate the lower boiling point, lower *molecular weight non-straight-chain paraffin hydrocarbons'present therein from the higher boiling point, highermolecular weight, non straight-chain parafiins present, or any two ormoreof the remaining portions canrbe combined into one or more composite fractions of non-strai'ght-chain-hydrocarbons and then frac tionated at asuitable temperature to separate isoand cyclo-paraflinic"hydrocarbonshaving boiling points below a selected boiling point from 'isoand'cyclo-paraflinic hydrocarbons having boiling points above that boiling point.

-- The invention is applicable to theseparation' of normal mixtures-composed -for..the most .part of such waxes. It

is equally applicable to the separation of such waxes when they are present in oily wax mixtures thereof, such as oily waxes which have been separated from petroleum lubricating oil distillates or Waxy deasphalted short residues by the usual lubricating oil dewaxing processes. The invention can also be used for the recovery and separation of normal parafiin waxes from isoand cycloparaffin waxes, with or without subsequent separation and recovery of the isoand cyclo-paraffin waxes, from highly paratfinic and paraffinic-naphthenic petroleum lubricating oil base stocks and distillates therefrom.

The present invention is based on the discovery that when a paraffinic petroleum waxy mixture of hydrocarbons is fractionated into narrow melting point fractions, that is, into fractions having a melting point range of about 4 C. to about 12 C., which fractionation can be effected by fractional crystallization of said mixture in a fluid state, either molten or dissolved in an organic solvent, the molecular weight of the highest molecular weight normal paraffin wax present in a given fraction is lower than the molecular weight of essentially all, if not all, of the isomeric paraffin waxes present, since the melting points of the paraffin waxes depend both on the molecular weight and on the molecular structure. The normal paraffins in each such fraction can then be readily separated as substantially pure normal paraffin waxes from the remainder of the fraction by fractionation according to molecular weight, for example, as by fractional distillation, since the boiling points of the normally solid paraffinic waxes depend primarily on the molecular weight thereof, or by fractional crystallization from such a solvent as will permit the crystallization of waxes according to molecular weights from hydrocarbon fractions having substantially the same melting point. The isomeric paraffin waxes remaining in the fractions can be separated into relatively lower molecular wei ht nonstraight-chain hydrocarbons and relatively higher molecular weight non-straight-chain hydrocarbons. Alternatively, those fractions of isomeric parafiin waxes above a specified melting point can be combined. and all those below that melting point can also be combined.

The fractionation of the waxy mixture according to meltin or freezing point can be effected by fractional crystallization. preferably in the presence of a suitable solvent or diluent. The fractionation of hydrocarbons according to melting or freezing points will be understood more readily by reference to the graphical representations of the melting point relationships shown in Figure I. The melting points of paraffin hydrocarbons are strongly dependent on the structures of the hydrocarbons. This aooears to be true particularly in the case of structurally different paraffin wax hydrocarbons, that is, paraffinic hydrocarbons containing about 16 or more carbon atoms per molecule, and especially those containing at least about 20 carbon atoms per molecule. Either branching or ring-closure within an aliphatic (parafiin) hydrocarbon of the ranges indicated is accompanied by a marked and significant drop in the melting point. It has been found that the melting point of a given n-parafiin wax h drocarbon containing n carbon atoms per molecule (n being at least about 16 and preferably 20 or more) is still significantly higher than the melting points of the non-straight-chain wax hydrocarbons containing n+3, and even n+4, carbon atoms per molecule. At a given melting point, then. there is a considerable difference between the molecular weights of the straight-chain wax hydrocarbons and non-straight-ch in wax hydrocarbons melting thereat. This is more readily seen from the portion of Figure I which shows the relationships between the melting points (as ordinates reading on the left side of the figure) and the number of carbon atoms per molecule (along the horizontal axis). The melting points for the straight-chain parafiin hydrocarbons are represented by the indicated solid curve, which is approximated by the indicated straight dashed line, corresponding to the linear equation:

Melting point C.)=7.5 +2.4 n, for integral values of n from about 20 to about 36, and wherein n is the number of carbon atoms per molecule of the straightchain paraffinic hydrocarbon. Thus there is a change of about 2.4 C. in melting pointfor a change of one carbon atom per molecule.

Whereas there is only a single normal paraffin hydrocarbon having the formula cnH2n+2 for a given value of 12, there are many isomeric branched-chain and 03/ paraifinic hydrocarbons having the same number of carbon atoms per molecule. The x points in Figure I are indicative of the melting points of such isomeric paraffins, the melting points of still many others of said isomers being below 16 C., the lowest point representable on the graph.

It will be seen from the foregoing, and by reference to Figure I, that a sharply cut, narrow melting point fraction of paraffinic hydrocarbons having an average melting point within the range of about 16 C. to about 76 C., and having a melting range of not over about 12 C., will define a mixture of parafiinic hydrocarbons containing as normal paraffinic hydrocarbons substantially only those which come within a carbon atom range of four and as isoparaffinic hydrocarbons those containing a greater number of carbon atoms than the highest molecular weight normal paraffin present. Similarly for mixtures of still higher melting parafiin waxes. Thus, a melting point fraction having a melting range of from about 51 C. to about 61 C., contains as normal paraffinic hydrocarbons only those which contain 24 to 28 carbon atoms per molecule, while containing essentially only'isoparaffinic hydrocarbons which contain at least 31 carbon atoms per molecule. From the foregoing, it will be understood, for example, that when it is desired to obtain a melting point fraction of paralfinic hydrocarbons containing as the highest molecular weight normal-paraffin, n-CzaHsa, in any substantial amount, the fraction will have an initial melting point of about or only a small amount above the melting point of the n-C28 paratfin, that is about 61 C., and the end melting point will be lower than 61 C. by a value of about 2.4- multiplied by n, n being the carbon atom range of thedesired fraction. Thus, if the range is to be two carbon atoms, then the temperature range is about twice 2.4, or about 5 C.; for a three carbon atom range, the temperature range is about 3 times 2.4, or 7.2, or from about 7 to about 8 C.; and not more than about 9 C., and for a four carbon atom range, the temperature range is about 4 times 2.4, or 9.6, or from about 9' to about 10 C., and not over about 12 C.

It is preferred to fractionate the waxy paraffinic hydrocarbon mixture into narrow melting range fractions, in the presence of a suitable solvent or diluent, particularly one which is not a preferential solvent for the n-paraffins or for the non-straight-chain paraffins. The solubility of a paraffin wax hydrocarbon in a solvent, for example, a polar solvent, such as oxygenated and/or halogenated hydrocarbon derivatives (methyl isobutyl ketone, carbon tetrachloride, ethylene dichloride), and mixtures thereof, and also in admixture with hydrocarbons suchv as benzene, toluene, light petroleum hydrocarbons, and the like, becomes exceedingly low at a given temperature below the solidification or melting point of the paraffin hydrocarbon, the given temperature being dependent upon and correlated with the melting point of the paraflin hydrocarbon and being substantially independent of the structural configuration of the paraffin. The respective solidification temperature of the different waxes are, of course, lowered below their melting points because of the solvency of the solvent. In general, in practical operations, wherein 2 to 10, and preferably 5 to 7, volumes of solvent are employed per weight of oil and/or wax, using consistent units in the c. g. s. system, as cubic centimeters of liquid per gram of solid, a temperature of 30 to 40 C. below the melting point of a given paraffin wax species insures almost complete insolubility of that given wax.

In order to show how well a wax mixture may be separated by fractional crystallization, a blend of equal parts of three practically pure normal paraffin hydrocarbons was fractionally crystallized from methyl isobutyl ketone. The hydrocarbons used were: (1) Normal C22H4s M. P.:45 C.; (2) Normal C2eHs4M. P.=56 C.; and (3) Normal C30HszM. P.=65.2 C.; their individual solubility curves in methyl isobutyl ketone are shown in Figure II. One part by weight of this blend was dissolved in 9 parts by weight of methyl isobutyl ketone and then very slowly cooled. The first wax crystals appeared at 39 C., which is exactly the temperature at which the pure Cami-I52 would start to crystallize if it were alone in solution (as a 3.3% solution). With stirring, the wax slurry was cooled to 28 C. and then quickly filtered through a precooled Buchner funnel (28 C. is approximately the temperature at which the C26H64 --washedfwith 3.3 parts of solvent.

. tion, 1943, and

gfJOSgSOtS w -:would-start "to crystallizefiif it were alone -in the solution).

I The-wax cake was washedyon the funnel with 3.3 parts =(precooled) methyl isobutyl ketone, firmly pressed, and finally-freed from solvent in a porcelain "dish. Thefiltrate wascooled further to 15 C. (the saturation temperature of n-C22H4 filtered and again After removing the solvent from 3 both the cakes and the final filtrate, the 1 following waxes were obtained:

Wax, M P.,

. The fractionation ofthe narrow melting range paraffinic,. waxy .petroleumfractions into wax products accord- .ling to molecular weight, as-by fractional distillation,

.{toseparate substantiallypure normalparafiin waxesfrom lthe.non-straight chain parafiinic hydrocarbons, and the coordinated combination thereof with the fractionation according tomelting points, will be more fully understood from the following description made with particu- ,lar referenceto the boiling point relationships shownin Figure I. The upper curve (normal parafiins) in Figure I was constructed from theboiling points of the normal parafiin hydrocarbons having from 19 to 36 carbon atoms per:molecule. The next solid curve thereunder repre- '.sents the boiling point-carbon atom permolecule relationship for all parafiinic hydrocarbons, the boiling points being averaged for all parafiins having a given carbonatom-per-molecule content. The boiling points reprethese boilingpoint curves are at '15 mm.

of mercury pressure. The numerical values forthe boil- ,ingpoints .of'the parafiins and for the melting points ofgthe straight-chainparafiins, from wh1ch the curves ,were constructed,-were taken from Physical Constants .of th Principal Hydrocarbons, by M. P. Doss, 4th edi- Physical Constants of Hydrocarbons, .gby; E. gEgloff,A. C'.- S..Mon0graph SeriesNo. .78, vol. II, 1 19 40. @Conversions of :boiling points from. reported values Jto 15mm. .of Hg pressure, where the reported .lvalue wasfor a -dififerentpressure-, were made. by utilizing the. conversion chart given byWatson and Wirth, in ,Ind. and Eng. Chem.,;Anal. Ed., vol. 7, page 73, January wTherupper dashed line inFig. I isa straight linewith a slope of-about 853C. (at -15 mm. Hg) per unit ,carbon-atom-per-molecule change and, as is readily seen, represents .within about 2 C. the boiling pointsof the ,norrnalnparafiins from C20 to C36, and also represents within;from about 2 C. to about 5 C.-the boiling-points ..of., substantiallyall-=of the'paraffinic hydrocarbons from .[Czo-toCse. As-indicated in Fig. I, this relationship is expressedby the equation:

3Boiling point C. at '15 mm. of Hg) =36+8;53 n

for-integralralues of n from about-20 to about 36, and ewherein n is the, number of carbon atoms'per molecule of ;the .paraifinic hydrocarbon. According to the dashed {,line' andthe equation, there is a'changein boiling points, ;.of-paraffinichydrocarbonshaving from about 20 to about 36. carbon atomspermolecule, at mm. of Hg pres- .sure, -of about 8.5 C. (15.3 F.) for each unit change in carbon atoms per molecule of the parafiin hydrocarbon. For. other pressures the boiling temperatures are changed for-the respective'hydrocarbons, as may be ,readily determined by use of the already indicated-conversion -method of Watson and Wirth, although the change ,in boiling temperatures with. change in carbon atom' per molecule content at-a given pressure-remains substantially thesame, namely about 8.5 C. per unit changein-carbonatomsper molecule. Thus, the boiling temperatureconverted to 760' mm. of Hg (atmospheric pressure), of n-C2sH54 is about 422 C. and of n-CsoHzs ,isabout 462 C., the difference being about 40 C. for .the Cze-lto Cxo range, a carbon atom-range .offour, or :about 10, C. per carbon atom difference.

.Inthe graph: in Figure I, various fractions aredefined by, horizontal dotted lines. Each 1 of the fractions so t defined covers-approximately a;melting point..range.of--

'C. *Each fraction also"covers a range of not more than about' 4 carbon atoms: per molecule of-the normal ferring to the graph, it-is seen,

about 48 C. contains fewer carbon atoms-per molecule and has alowerboilingpoint than the-lowest molecular weight and 'lowestboiling non-straight chain paraffin hydrocarbon isomer '(i.1 e.,'1sooreyclo-paraflim hydrocarbon) having a melting point'of 40 C. or even 38 C. It will be further noted from the graphthatthere are many more=isomeric=iso-f and. cyclo-paraflins melting between about'40 C. and 48 C. which contain a still greaternumber'of carbon atoms per-molecule and-have a still higher boiling point thanthe normal parafiinhydrocarbon meltingat 48 C. These other isomeric: paratfins constitute av-large' proportion of-the totalisomeric parafiin content of any actual petroleum disti1late"fraction of a petroleum oil stock containing bothnormal and isomeric parafiin hydrocarbons.

. Although the above-indicated diiferencesin molecular weights of paralfin wax hydrocarbons having 'm'elting points within arelatively narrow melting range makeit such mixtures of paraifin wax hydrocarbons by a process of :fractional distillation, based on' boiling point differences, it is also possible to separate such mixtures by a process of recrystallization from a solvent which permits the crystallization of-waxes according to 'molecular Weight from hydrocarbon fracti'ons having substantially the same melting points. The solubility -of' a paraflin- Wax hydrocarbon in'a solventfifor example, a polar solvent suchas'methyl'ethyl ketone, is

relatedto a the molecular weight' of E the paraflinhydrocarbon, .the lowest molecular-"weight parafiin'hydrocarbon being the most soluble inthe solvent at a given temperature. The effect of the presence of methyl ethyl .ketone on the solidification'temperatures of representati-vestraight-chain vparaffinwaxes having-the same melting'point"but'dif- =ferent molecular weights. Referring to parafiin waxes and non-straight-chain Fig. III, 'A'is a normal: parafiin hydrocarbon wax having'a' 'molecular weightof 282;+B 1s a non-straighbchain-parafiin wax having a molecular weight of chain paraffin wax having Each of the waxes has a 490; and C is a non-straighta molecular-weight of 5'40. melting point of V 36 'C. The solubilities of each wax in methyl ethyl ketone at various temperatures'are shown-by the indicated curves.

Having'described the invention in a general manner 7 and havingdiscussed various-factors related'to the=inventron, and

their correlation in the application of the invention, it will be better understood from a moredetailed description of a more specific embodiment thereof. 'A more detailed description will be made with reference, forexample, to a so-called -slack'wax or crude wax, produced and obtained in the art and which'is usually an oily :mass ofa mixture predominating in parafiin waxes, including 'both n-parafiins 'and iso-' and' cycloparaflins, the proportions -thereof depending on the nature of the petroleumstockfrom-which the slack WiiX'lS'Obtained. A representative total-lubricating oil'distillate a boiling range of from about 180 C. to about 310 C. at-7 mm. of Hgpressure, corresponding to from about 200 C. to about 330 C. at 15 mm; of Hg pressure, and may have a range for the number of carbon atoms per molecule of C20 to Cssor C35 and'generally will contain from about 40% to'about 80% of wax and 20% to-60%. of oil, the melting'point of the wax ranging from-about -F. to about 'F., depending on the relative proportions-of wax and oil and also on the'relative proportions of the various molecular species of wax molecules-present.

Now, the first essential step, in accordance with'the present invention, is to-fractionate the slack wax into a number of'narrow' melting range fractions,-at least one fraction of which, and preferably all fractions, containing paraflin hydrocarbon waxes such that the molecular weight of the lowest molecular weight isomeric parafiin wax in said fraction is higher than thehighest molecular weight of the lowest molecular weight isometric parafi'in wax in each such fraction havinga range of carboniatoms per molecule of not more than four and preferably not more than two or three. In general, it will be satisfac- .in has a highermolecular'weightilthan the 'highestzmolecular weight n-paraffin wax present.

The separation of the wax content of the slack wax into the indicated fractions may be effected either with or without a prior separation of any or a substantial proportion of the oil con- 'tent thereof.

That is, the slack wax may be de-oiled by any suitable method, such as sweating and/or solvent de-oiling, first to remove substantially all or a substantial proportion of the oil content thereof, to produce a scale wax and the separated wax then fractionated, as by fractional crystallization, into the desired fractions. It will also be understood that the total lubricating oil distillate stock can be tdewaxed at successively lower temperatures, with separation of wax from oil at each dewaxing temperature, to obtain the desired fractions.

The fractionation of the slack wax into narrow melting :range fractions is preferably effected by fractional crystallization in the presence of a suitable solvent or diluent. Suitable diluents include lighter petroleum fractions, such as kerosene, gasoline, naphtha, propane, butane. etc., fractions. as well as various organic liquids such as halogenated hydrocarbons (chloroform. carbon tetrachloride, ethylene dichloride, ethvlidene dichloride. etc). ethers (ethyl ether. ethyl propvl ether, methvl isobutvl ether, and the like). ketones (acetone. methvl is butvl ke one, etc). aromatic h drocarbons (benzene. to uene, xylene, and the like), and vari us mixtures there f.

After havin adiusted the temperature of the slack wax to solidify a narrow melting range wax fraction, the resultin mixture or slurry is separated. as bv fil r ion or centrifugation or the like into a separated solid fra ti n having a narrow melting ran e and a sen rated liquid frac ion containin he lo er mel in con ti en s.

Now. assuming for clarity of discussi n that the s ack wax has been fractionated to pr duce at ast one narr w meltin ran e slack w x fraction as defined ab ve. he next e ential s ep of the process is to senar te the relatively lower molecular weight (i. e., lower b iling) normal parafl'ln hydrocarbons ther in from the relativel hi er molecular wei ht (i. e., hi her boiling) isomeric par flin hydrocarbons therein. The desi ed se ra i n is preferably effected by fractionallv distillin the indicated Fraction at a temperature between the boilin noint of the hi h st molecular Wei ht (i. e.. hi hest b ilin norm l paraffin wax therein and the lowest molecu ar wei ht (i. e.. lowest hoilin l isomeric parafiin wax therein thereby removin all or sub antially all of he normal narafiin waxes as distillate. The rem ining linuid fraction can be further separated at a sti l hi her temperature to se ar te the relatively lower mo ecul r wei ht isomeric paraffin waxes fr m the relatively higher molecular weight isomeric parafi'ln waxes.

Tt will be understood. particularl b reference to Fi .I, th t a substantial separation. which m y be e tirely satisfactor in some c ses. de ending on the initial wax m teri l. the desired wax products, etc, may be accomplished by minor deviations from the above indicated combination of o erations. For example. in s me cases the composition of a iven fr tion m be such that the temperature of se ration of the strai h -chain and nonstrai ht-chain p r flin waxes mav actua l be be w the boiling point of the hi hest boiling norm l oarafiin wax present. and still satisfactory products will be obt ined. Conversel in some cases the temoer ture of se aration ma be above the b iling point f the lowest b ili g nonstrai h -chain nar fiin x. Simil rly. as will be seen from Fi l, sli htly wider r n e fr ctions may be resolved int satisfactor strai ht-ch in and non-strai ht chain parafiin wax products by application of the i vention. even in those cases where the molecular wei ht of the hi h st molecular wei ht normal n rafiin wax is not necessarily below the mo ecular wei ht of the lowest molecular weight non-straight-chain nar ffin wax present, provided the resulting overlapping of molecular wei hts does not involve more than about prefer ably not more than of the total paraffin wax content of the fraction involved, or not more than about 10% based on the normal paraffin wax content thereof. Thus, in general, the selection of a range of the paraffin wax hydrocarbons for a given fraction and/or the selection of a suitable temperature for separation of the normalfrom the isomeric-paraflin waxes therein are correlated so that the paraffin wax content of one of the separated products will be such that the ratio of the 8 weight of one of the types of paraflin waxes therein to the other type will be at least about to 10, that 1s, 90% purity on the wax basis with respect to either the normalor the isomeric-paraffin wax.

The present invention is applicable to the treatment of various types of paraffinic wax mixtures, including slack waxes (as described above), slop waxes, scale waxes, short and long wax residues as obtained by processes well known to the art, etc. The fractionation of the wax mixture into the required fractions to be processed in accordance with the invention may be made by any suitable method, such as by fractional crystallization, and in the absence or presence of a suitable solvent or diluent. In the fractionation, sufficiently narrow range of melting points in a cut may be tested empirically by a small-scale test on an aliquot part of the cut to determine that, when the resulting solution is heated appreciably above the boiling point of the highest boiling n-paraffin wax therein, there is substantially complete separation of the n-paraifin wax therein from the non-straight-chain waxes in the cut. Tests upon the resulting separated wax to show the structural character of the wax are readily made by persons skilled in the art making use of such conventional tests as that for ring value and for asymmetric value.

Various modifications of the hereinabove-described techniques of manipulation as are known in the art may be utilized in the practice of the invention. Thus, the separation of solid from liquid phases may be effected by pressure filtration, vacuum filtration, centrifugation, etc. The cooling operations effecting wax crystallization may be stepwise, if desired, and also with or without shock chilling with stepwise introduction of supercooled dilutent and/0r selective solvent so as to effect a control over the crystal formation.

I claim as my invention:

1. A process for the separation of straight-chain paratfin waxes from paraffinic waxy mixtures comprising both straight-chain paraffin waxes and non-straight-chain paraffin waxes and wherein there is an overlapping of the melting points of the two types of waxes present, which process comprises the steps of: separating from said waxy mixture by crystallization a plurality of narrow melting range fractions at least one of which contains both straight-chain and non-straight-chain paraffin waxes and has a melting point range of not more than about 12 C., whereby the boiling point of the highest boiling straightchain parafiin wax present is lower than the boiling point of the lowest boiling non-straight-chain paratfin wax present therein; and separating said fraction by distillation into a first relatively lower boiling, lower molecular weight fraction composed substantially entirely of the straight-chain parafiin waxes present in said fraction, and a second relatively higher boiling, higher molecular weight fraction composed substantially entirely of the non-straight-chain parafiin waxes present therein.

2. A process for the separation of straight-chain paraffin waxes from parafiinic waxy mixtures comprising both straight-chain paraffin waxes and non-straight-chain paraflin waxes and wherein there is an overlapping of the melting points of the two types of waxes present, which process comprises the steps of intimately mixing said waxy mixture with a non-viscous diluent which is non-reactive therewith; separating from the resulting mixture by crystallization a plurality of fractions each of which has a melting point range of not more than about 12 C., and contains both straight-chain paraffin waxes and non-straight-chain paraffin waxes, whereby the boiling point of the highest boiling straight-chain paraflin wax present in a given one of said fractions is lower than the boiling point of the lowest boiling non-straight-chain paraffin wax present; and separating each of said fractions by distillation into a first relatively lower boiling, lower molecular weight fraction composed substantially entirely of the straight-chain paraflin waxes present in said fraction, and a second relatively higher boiling, higher molecular weight fraction composed substantially of the non-straight-chain paraflin waxes present therein.

3. A process for the separation of straight-chain paraffin waxes from paraffinic waxy mixtures containing both straight-chain paraffin waxes and non-straight-chain paraffin waxes ranging from about C20 to about C35 and wherein there is an overlapping of the boiling points of the two types of waxes present, which comprises the steps of: separating from said waxy mixture by crystallization .alplurality of narrow melting. range fractions. at least one .or whichha'sa melting-point ran'ge of not more than'about 12 C; and containslboth straight chairi and non-straightchainl rparafin. waxes, L the 'numberl'of carbon :atoms'; per molecule of the straight-chainrparaflin wax'estherein differin'g by not. more thanfouncarbo'ri atoms,.whe rebythe bolling point .of the highest.molecular weight. straightchain; ,paraffin .waxpre'sent'iis lower than ithhoiling point of the lowest molecular weight non-.straight-chain.paraf- ;finf wax present. therein; separating said fraction. by i dis- 1 tillationf into a .first. relativelyvlowr boiling, lower molecularweight fraction; composed of substantially all of the straight-chainparaffin. waxes therein and a second relaiV.elyhigherboiling, -.,higher molecular .weightsfraction composed of. substantially all ofwthe..non-straight-chain paiafitln .waxes therein; and furtherseparating.byzdistilla- ,ti'on said second relatively. .higher. boiling fractioncompo s'ed of substantially all of the non-.straight chain paraf- -finwaxesi therein into a1.firsti fraction composed of relatively lower boiling, lowerfmolecular weight non-straight- ..chain paraflin waxes andasecond fraction composed of .r'elativelyihigher boiling, higher molecular weight nonstraight-chain paraffin waxes.

'4. A process for theseparation iof.straight-chain paraf- .-fin. waxes from parafiinic {waxy} mixtures containing .both straight-chain paraflin waxes and. non-straight-chainpar- ,afiintwaxes ranging from aboutqczo .to about: C35 and wherein there is an overlapping ofi-theboiling points-of the two types of waxes present, which comprises the steps of: intimately mixing said waxyl'mixtureawith a nonviscous diluent which is. on-reactive,therewith, separating from the resulting mixture by fractional crystallization ,a pluralitymof fractions at'least vone of which-has a m l ing r nge .ofnot. morethanaboutQ? C. andco'ntains both straightrchain and vnon:straight-chain paraflin-Zwaxes, 1

the, number, of carbon atoms. of athe straight-chain. paraffin waxes therein difiering by not more than three carbon atoms, whereby the boiling point of the highest molecular weight straight-chain paraffin wax is lower than the boiling point of the lowest molecular weight nonstraight-chain parafiin wax present therein; and separating said fraction by distillation into a first relatively lower boiling fraction composed of substantially all of the straight-chain paraffin waxes therein and a second relatively higher boiling fraction composed of substantially all of the non-straight-chain parafiin waxes therein.

5. A process for the separation of straight-chain paraffin waxes from non-straight-chain parafiin waxes in an oily slack wax stock having a boiling range of from about 180 C. to about 310 C. at 7 mm. of Hg pressure and containing paraffinic waxes ranging from about C20 to about C25, which process comprises intimately mixing said slack wax with a non-viscous diluent non-reactive therewith; separating from the resulting mixture by fractional crystallization a plurality of narrow melting range fractions at least one of which has a melting point range of not more than about 12 C. and contains both straightchain and non-straight-chain hydrocarbon waxes, the number of carbon atoms per molecule of said straightchain hydrocarbon waxes therein differing by not more than four carbon atoms, whereby the molecular weight of the highest molecular weight straight-chain wax is lower than the molecular weight of the lowest molecular Weight non-straight-chain paraflin wax present therein; and separating said fraction by distillation into a first relatively lower boiling fraction composed of substantially all of the straight-chain parafiin waxes therein and a second relatively higher boiling fraction composed of substantially all of the non-straight-chain paraffin waxes therein.

6. A process for the separation of straight-chain paraffin waxes from paraffinic waxy mixtures containing both straight-chain parafiin waxes and non-straight-chain paraffin waxes ranging from about C20 to about C35 and wherein there is an overlapping of the melting points of the two types of waxes present, which comprises the steps of: separating from said mixture by fractional crystallization a plurality of fractions at least two of which have a melting range of not more than about 12 C. and contain both straight-chain and non-straight-chain parafiin waxes, whereby the boiling point of the highest molecular weight straight-chain paraflin wax is lower than the boiling point of the lowest molecular weight non-straight-chain paraffin wax present therein; separating each of said fractions by distillation into a first relatively lower boiling, lower straight-chain 'paraffin wax present therein; and separating molecular. weightafractioni composed of substantiallyall .1df the..-straigh chain,paraffin..waxesi.therein and a second i'elatively higher boiling,- higher molecular weight'gfracftion composed of substantially :all of the non-straight- =-Cl1a1l1 paraffin waxes therein; combining .atleast substantial fin Waxes from'paraffinic waxy mixture comprlsing both straight-chain paraffin waxes-and non-straight-chain, paraffin waxes and wherein there is an overlapping of v the melting points of the two types-of waxes present, which process comprises the steps of: separating from said waxy "mixture by crystallization a plurality of narrow melting range -fractions at leastone of which contains both straight-chain and-non-straight-chainparaffin waxes and has amelt'in'g point range of not morethan about 12C., whereby th'e'molecular weight of thehighest molecular Weight straight-@chain paratfin wax-present is lower than the molecular weight of the lowest molecular weightnonsaid-fract ioninto a first relativelylower molecularweight fraction composedsubstantiallyentirely of'the straightchain paraflin waxes-present in saidjfraction, and a second .relatively higher molecular-weightfraction composed subantiallyentirely of I thenon-straight-chain paraflin waxes ,present therein.

{8; .In a process for dewaxing a-waxy mineral oilwhich contains -both n-paraifinhydrocarbon waxes and isomers thereof extendingoyer the range of C20 to C35 hydrocarbons, and wher ein there is anoverlapping of =the melting points of the two different types of waxes present, the improvement which comprises the steps of: intimately mixing said waxy mineral oil with an oil-miscible organic polar solvent which is substantially immiscible with solid wax at dewaxing temperatures; separating from the resulting oil-solvent mixture by dewaxing at successively decreasing temperatures a plurality of narrow melting range fractions at least one of which has a melting point range of not over about 12 C. and contains both straightchain and non-straight-chain parafiin hydrocarbon waxes, whereby the molecular weight of the highest molecular weight straight-chain parafiin wax present is lower than the lowest molecular weight non-straight-chain paraflin wax present; and separating said fraction by distillation into a first relatively lower boiling fraction composed of substantially all of the straight-chain paraffin waxes therein and a second relatively higher boiling fraction composed of substantially all of the non-straight-chain paraffin waxes therein.

9. In a process for dewaxing a waxy mineral oil which contains both n-paraflin hydrocarbon waxes and isomers thereof extending over the range of C20 to C25 hydrocarbons, and wherein there is an overlapping of the melting points of the two different types of waxes present, the improvement which comprises the steps of: intimately mixing said waxy mineral oil with an oil-miscible organic polar solvent which is substantially immiscible with solid wax at dewaxing temperatures; separating from the resulting oil-solvent mixture by dewaxing at successively decreasing temperatures a plurality of narrow melting range fractions at least one of which has a melting point range of not over about 9 C. and contains both straightchain and non-straight-chain parafiin hydrocarbon waxes, the number of carbon atoms per molecule of the straightchain paraffin hydrocarbon waxes difiering by not more than three carbon atoms, whereby the molecular weight of the highest molecular weight straight-chain parafiin wax present is lower than the lowest molecular weight non-straight-parafiin wax present; and separating said fraction by distillation into a first relatively lower boiling, lower molecular weight fraction composed of substantially all of the straight-chain paraflin waxes therein and a second relatively higher boiling, higher molecular weight fraction composed of substantially all of the non-straightchain paraffin waxes therein.

10. In a process for dewaxing a waxy mineral oil which contains both n-paraflln hydrocarbon waxes and isomers thereof extending over the range of C20 to C35 hydrocar- "hens, and wherein there is an overlapping of the melting points of the two difierent types of waxes present, the

improvement which comprises the steps of: intimately mixing said waxy mineral oil with an oil-miscible organic polar solvent which is substantially immiscible with solid wax at dewaxing temperatures; separating from the resulting oil-solvent mixture by dewaxing at successively decreasing temperatures a plurality of narrow melting range fractions at least one of which has a melting point range of not over about 12 C. and contains both straight- I chain and non-straight-chain paraffin hydrocarbon waxes,

whereby the molecular weight of the highest molecular weight straight-chain paraflin wax present is lower than ;.the lowest molecular weight non-straight-chain paraffin wax present; and separating said fraction by distillation into a first relatively lower boiling fraction composed of substantially all of the straight-chain parafiin waxes therein and a second relatively higher boiling fraction composed of substantially all of the non-straight-chain parafiin waxes therein, and further separating by distillation said second relatively higher boiling fraction into a first fraction composed of relatively lower boiling, lower molecular weight non-straight-chain paraflin waxes and a second fraction composed of relatively higher boiling, higher molecular weight non-straight-chain parafiin waxes.

11. In a process for dewaxing a waxy mineral oil which contains both n-paratfin hydrocarbon waxes and isomers thereof, and wherein there is an overlapping of the melting points of the two difierent types of waxes present, the improvement which comprises the steps of separating from said waxy mineral oil by dewaxing at successively decreasing temperatures a plurality of narrow melting range fractions at least oneof which has a melting point range of not over about 12 C. and contains both straightchain and non-straight-chain paraflin hydrocarbon waxes, whereby the molecular weight of the highest molecular the lowest molecular weight non-straight-chain paraffin -wax present; and separating said fraction by distillation into a first relatively lower boiling, lower molecular weight fraction composed of substantially all of the straight-chain paraffin waxes therein and a second relatively higher boiling, higher molecular weight fraction composed of substantially all of the non-straighbchain paraffin waxes therein.

12. A process for dewaxing a waxy mineral oil which contains bothn-paraffin hydrocarbon waxes and isomers thereof, and wherein there is an overlapping of the melting points of the two different types of waxes present, the improvement which comprises the steps of: separating from said waxy mineral oil by dewaxing at successively decreasing temperatures a plurality of narrow melting range fractions at least one of which has a melting point range of not over about 12 C. and contains both straightchain and non-straight-chain parafiin hydrocarbon waxes, whereby the molecular weight of the highest molecular weight straight-chain paraffin wax present is lower than the lowest molecular weight non-straight-chain paratfin wax present; and separating said fraction into a first relatively lower molecular weight fraction composed of substantially all of the straight-chain paraffin waxes therein and a second relatively higher molecular weight fraction composed of substantially all of the non-straight-chain paraffin waxes therein.

References Cited in the file of this patent UNITED STATES PATENTS 1,937,518 Henderson et a1 Dec. 5, 1933 2,229,659 Carr Jan. 28, 1941 2,467,959 Bowman et a1 Apr. 19, 1949 2,603,589 Schaerer July 12, 1952 

1. A PROCESS FOR THE SEPARATION OF STRAIGHT-CHAIN PARAFFIN WAXES FROM PARAFFINIC WAXY MIXTURES COMPRISING BOTH STRAIGHT-CHAIN PARAFFIN WAXES AND NON-STRAIGHT-CHAIN PARAFFIN WAXES AND WHEREIN THERE IS AN OVERLAPPING OF THE MELTING POINTS OF THE TWO TYPES OF WAXES PRESENT, WHICH PROCESS COMPRISES THE STEPS OF: SEPARATING FROM SAID WAXY MIXTURE BY CRYSTALLIZATION A PLURALITY OF NARROW MELTING RANGE FRACTIONS AT LEAST ONE OF WHICH CONTAINS BOTH STRAIGHT-CHAIN AND NON-STRAIGHT-CHAIN PARAFFIN WAXES AND HAS A MELTING POINT RANGE OF NOT MORE THAN ABOUT 12* C., WHEREBY THE BOILING POINT OF THE HIGHEST BOILING STRAIGHTCHAIN PARAFFIN WAX PRESENT IS LOWER THAN THE BOILING POINT OF THE LOWEST BOILING NON-CHAIN PARAFFIN WAX PRESENT THEREIN; AND SEPARATING SAID FRACTION BY DISTILLATION INTO A FIRST RELATIVELY LOWER BOILING, LOWER MOLECULAR WEIGHT FRACTION COMPOSED SUBSTANTIALLY ENTIRELY OF THE STRAIGHT-CHAIN PARAFFIN WAXES PRESENT IN SAID FRACTION, AND A SECOND RELATIVELY HIGHER BOILING, HIGHER MOLECULAR WEIGHT FRACTION COMPOSED SUBSTANTIALLY ENTIRELY OF THE NON-STRAIGHT-CHAIN PARAFFIN WAXES PRESENT THEREIN. 